The Siemens SIRIUS 3RV1901-1B is a lateral auxiliary switch that clips onto the side of SIRIUS 3RV circuit breakers in frame sizes S00, S0, S2, and S3. It gives you two normally-open (2 NO) instantaneous contacts for signaling the breaker's tripped or closed state back to a PLC or indicator lamp — no contactor or separate relay needed to mirror the breaker position.
Switching capacity and what those current ratings mean
The contacts are rated for 10 A maximum, but that's the thermal current — the real-world switching capacity depends on voltage and load type. At 24 V you get 2 A; at 110 V it drops to 0.5 A; at 230 V it's 4 A; at 400 V it's 3 A; and at 690 V it's 10 A. The AC-15 rating at 690 V is 1 A, which is the inductive load curve for solenoid or contactor coils at that voltage. For a control transformer or resistive load, use the higher thermal numbers; for a motor contactor coil at 400 V, stay within the 3 A AC-15 curve.
Mounting and wiring — fits the panel, not the rail
This switch uses plug-in fixing — it snaps onto the side of the breaker, not onto a DIN rail. That's the lateral design: it adds width to the breaker assembly without eating up rail space. The 9.5 mm width means it tucks in tight alongside the breaker. Wiring is via screw-type terminals; the clamping range accepts 2x (0.5 to 1.5 mm²) solid or 2x (0.75 to 2.5 mm²) stranded per terminal, which covers most control-circuit runs. Strip length and torque follow standard Siemens terminal practice for this class.
Environmental limits and compliance
No UL or CSA listing is stated in the available documentation; the part carries Siemens SIRIUS branding and is designed to IEC/EN standards for the 3RV breaker family. Compliance documentation (RoHS, REACH) is standard for current Siemens industrial control products.